• Hill and Griffith

20 Green Sand Casting Defects and Their Suggested Remedies

Originally published January 2017 by Mechanical Engineering


Probable causes and suggested remedies of various casting defects such as blow holes, shrinkage, porosity, misruns, hot tears, mental penetration, cold shuts, cuts and washes, inclusions, fusion, drops, shot metal, shift, crushes, rat-tails, swells, hard spot, run out, fins and fash, spongings and warpage are given in the below table.



Photo credit: Green Mechanic


S.no

Name of Casting Defect

Probable Causes

Suggested Remedies

1

Blow holes

  • Excessive moisture content in molding sand.

  • Rust and moisture on chills

  • Cores not sufficiently baked.

  • Excessive use of organic binders.

  • Molds not adequately vented.

  • Molds not adequately vented.

  • Molds rammed very hard.

  • Control of moisture content.

  • Use of rust free chills, chaplet and clean inserts.

  • Bake cores properly.

  • Ram the mold less hard.

  • Provide adequate venting in mold and cores.

2

​Shrinkage

  • ​Faulty gating and risering system.

  • Improper chilling.

  • ​Ensure proper directional solidification by modifying gating, risering and chilling.

3

Porosity

  • ​High pouring temperatures.

  • Gas dissolved in metal charge.

  • Less flux used.

  • Molten metal not properly degassed.

  • Slow solidification of casting.

  • High moisture and low permeability.

  • ​Regulate pouring temperature.

  • Control metal composition.

  • Increase flux proportions.

  • Ensure effective degassing.

  • Modify gating and risering.

  • Reduce moisture and increase the permeability of mold.

4

Misruns

  • ​Lack of fluidity ill molten metal.

  • Faulty design.

  • Faulty gating.

  • ​Adjust proper pouring temperature.

  • Modify design.

  • Modify gating system.

5

​Hot Tears

  • ​Lack of collapsibility of core.

  • Lack of collapsibility of mold.

  • Faulty design.

  • Hard ramming of mold.

  • ​Improves collapsibility of core and mold.

  • Modify casting design.

6

Mental penetration

  • ​Large grain size and used.

  • Soft ramming of mold.

  • Molding sand or core has low strength.

  • ​Use sand having finer grain size.

  • Provide hard ramming.

  • Suitably adjust pouring temperature.

7

Cold shuts

  • ​Lack of fluidity in molten metal.

  • Faulty design.

  • Faulty gating.

  • ​Adjust proper pouring metal.

  • Modify design.

  • Modify gating system.

8

Cuts and washes

  • ​Low strength of mold and core.

  • Lack of binders in facing and core stand.

  • Faulty gating.

  • Improve mold and core strength.

  • Add more binders to facing and core sand.

  • Improve gating.

9

Inclusions

  • ​Faulty gating.

  • Faulty pouring.

  • Inferior molding or core sand.

  • Soft ramming of mold.

  • Rough handling of mold and core.

  • Modify gating system.

  • Improve pouring to minimize turbulence.

  • Use of superior sand of good strength. Provide hard, ramming.

10

Fusion

  • ​Low refractoriness in molding sand.

  • Faulty gating.

  • Too high pouring temperature of the metal.

  • Pouring facing sand.

  • ​Improve refractoriness of sand.

  • Modify gating system.

  • Use Lower pouring temperature.

  • Improve the quality of facing sand.

Read more about the next 10 Green Sand Casting defects and their remedies at Mechanical Engineer.


 

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